1. Field of the Invention
The present invention relates to a substrate bonding apparatus for a liquid crystal display (LCD) panel, and more particularly, to a substrate-chucking electrostatic chuck (ESC) which is sub-divided into three different groups of electrostatic blocks, to uniformly chuck the substrate, and a substrate bonding apparatus and method for an LCD panel using the electrostatic chuck.
2. Discussion of the Related Art
With the progress of information-dependent society, the demand for various display devices has increased. To meet such a demand, efforts have recently been made to research flat panel display devices such as liquid crystal display devices (LCDs), plasma display panels (PDPs), electro-luminescent displays (ELDs), vacuum fluorescent displays (VFDs), and the like. Some types of such flat panel display devices are being practically applied to various appliances and products for display purposes.
In particular, LCDs have been used as a substitute for cathode ray tubes (CRTs) in association with mobile image display devices because LCDs have advantages of superior picture quality, lightness, thinness, and low power consumption. Thus, LCDs are currently the most widely used. Various applications of LCDs are being developed in association with not only mobile image display devices such as monitors of notebook computers, but also as TV monitors to receive and display broadcast signals.
Although LCDs have been variously developed so that they can be used as picture display devices in various fields, improving the quality of images in such LCD is made difficult by attempting to improve the above-mentioned features and advantages.
Accordingly, successful applications of such LCDs to diverse image display devices depend on whether or not the LCDs can realize desired high picture quality including high resolution, high brightness, large display area, and the like, while maintaining desired characteristics of lightness, thinness, and low power consumption.
Methods for manufacturing the above-mentioned LCDs are mainly classified into liquid crystal injection type methods and liquid crystal dispensing type methods. In the liquid crystal injection method, a sealant pattern is written on one of upper and lower substrate such that the sealant pattern has an injection port. Thereafter, the substrates are bonded to each other under a vacuum condition. A liquid crystal material is then injected into a space defined between the substrates through the injection port. In the liquid crystal dispensing method, one substrate is prepared on which a liquid crystal material has been dispensed. Another substrate is prepared on which a sealant pattern is formed such that the sealant pattern extends completely along the peripheral edge of the substrate without forming an injection port. Thereafter, the latter substrate is arranged on the former substrate under a vacuum condition such that they are aligned with each other. The aligned substrates are then bonded to each other. Such a liquid crystal dispensing method is disclosed in Japanese Patent Application Nos. Heisei 11-089612 and Heisei 11-172903.
The liquid crystal dispensing method has an advantage in that the liquid crystal dispensing method uses a reduced number of processes in accordance with elimination of certain processes required in the liquid crystal injection method, for example, processes for forming a liquid crystal injection port, injecting a liquid crystal material, and sealing an injection port, and thus, does not use or require equipment for those processes.
For this reason, active research has recently been made to provide more efficient equipment for use in the liquid crystal dispensing method.
For example, the applicant proposed a substrate bonding apparatus for an LCD panel through Korean Patent Application No. 2002-71366 (Filing date: Nov. 16, 2002).
Where it is desired to bond an upper substrate (or a lower substrate) to a lower substrate (or an upper substrate) coated with a sealant along the peripheral edge of the lower substrate, and dispensed with a liquid crystal material, using the substrate bonding apparatus proposed by the applicant, the upper substrate is first chucked to an upper electro-static chuck (ESC), and is then lowered such that the upper substrate approximates to the lower substrate. The upper ESC is then turned off, thereby releasing the upper substrate which is, in turn, laid on the lower substrate. In this state, the substrate bonding apparatus performs a venting process to bond the upper and lower substrates to each other.
In the above-mentioned related art substrate bonding apparatus, the upper ESC thereof includes a plurality of electrostatic blocks classified into two groups to which different voltages are supplied, respectively.
Each electrostatic block of each electrostatic block group chucks a substrate using an electrostatic chucking force generated when a voltage associated with the electrostatic block group is applied from a voltage source to the electrostatic block. The electrostatic chucking force is released when the voltage applied to the electrostatic block is cut off. In accordance with the release of the electrostatic chucking force, the chucked substrate is separated from the upper ESC to fall down.
However, the ESC used in the above-mentioned related art substrate bonding apparatus has a problem in that uniformity of chucking of a substrate and release of the chucked substrate cannot be enhanced because the chucking and release are achieved by simply applying voltages to the associated electrostatic blocks and simply cutting off the applied voltages, respectively. That is, the related art ESC cannot uniformly chuck the substrate using two different groups of electrostatic blocks because the substrate may be bent due to its weight. Furthermore, the substrate may not fall down uniformly when the voltages applied to the ESC are cut off.